1. Technical Field
Example embodiments of the present invention relate in general to a mobile telecommunication technique, and more particularly, to a method of controlling interference of a femtocell to have the femtocell itself avoid the interference on a macrocell and also have the macrocell not be interfered with by the femtocell at the time of initial installation and management of the femtocell in an environment where the macrocell and the femtocell overlap.
2. Related Art
Controlling inter-cell interference becomes an important issue in a case of a 4th mobile telecommunication system using an orthogonal frequency division multiplexing (OFDM) technique, and in particular, solving interference between a macrocell and a femtocell becomes an important issue in a heterogeneous network where the macrocell and the femtocell overlap.
Frequency allocation schemes for the femtocell and the macrocell are broadly classified into two types. One is a co-channel frequency allocation scheme in which the macrocell and the femtocell share the same frequency band, and the other is an orthogonal channel frequency allocation scheme in which the macrocell and the femtocell use the full frequency band with no frequency overlapping between the macrocell and the femtocell.
In the former case, although there is interference between the macrocell and the femtocell, a frequency use ratio is high. In the latter case, although there is no interference between the macrocell and the femtocell in the full frequency band, the frequency use efficiency is poor.
That is, in the case of the co-channel frequency allocation scheme, solving the interference between the macrocell and the femtocell becomes an important issue. In particular, there is a difference between transmission powers of respective base stations of the macrocell and femtocell, and the interference from the macrocell to the femtocell is negligible due to a relative distance, however, the interference from the femtocell to the macrocell may be problematic.
Techniques of controlling the interference between the macrocell and the femtocell according to the related art may employ a coordination method between the macrocell and the femtocell. Such a coordination method allows finer tuning to be performed between the macrocell and the femtocell. However, considering actual femtocell deployment situations (e.g., open/closed/hybrid), exchanging messages for coordination between numerous femtocells and the macrocell is not feasible in practice. The coordination method causes many signaling loads on the network, an algorithm for handling the signaling loads has a high level of complexity, and femtocell costs increase significantly. Further, the macrocell must also be upgraded.